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D E E R E & A U L T RECEIVED <br /> CONSULTANTS, INC.- <br /> MAY 17 2019 <br /> DIVISION OF RECLAMATION <br /> TECHNICAL MEMORANDUM o <br /> MINING AND SAFETY �DM1 vcFti <br /> TO: Mark A. Steen(Colorado Milling Company LLC) . <br /> .� 38427 c <br /> FROM: Christoph Goss PhD, P.E. <br /> DATE: May 15, 2019 `rs/pj �ENG� <br /> RE: Times Mine Bulkhead Evaluation <br /> D&A Job No. 0788.001.00 <br /> This technical memorandum is in response to a request by Colorado Milling Company, LLC to <br /> evaluate the Times Mine Bulkhead at the Gold Hill Mill site. <br /> BACKGROUND <br /> The Gold Hill Mill is an existing mineral processing facility in Boulder County, Colorado, near <br /> the town of Gold Hill (MLRD Limited Impact 110(2) Permit No. M-1994-117). The general <br /> location is shown in Figure 1. In December 2017, Colorado Milling Company, LLC (CMC) <br /> submitted an amendment to add several components to the permitted site. These include the Left <br /> Hand Creek Pump Station, Gold Mill Pipeline Easement, and Times Mine Adit Portal. Since the <br /> amendment application submittal, the Colorado Division of Reclamation, Mining, and Safety <br /> (DRMS) has issued three Adequacy Review letters dated 1/26/2018, 12/21/2018, and 1/14/19. <br /> CMC has responded to Adequacy Review letters 1 and 2 on 12/8/2018 and 1/4/2019, <br /> respectively. Based on this correspondence, there are various outstanding issues to be evaluated <br /> and addressed. Deere & Ault Consultants Inc, (D&A) has evaluated those issues related to the <br /> Times Mine Bulkhead. <br /> In 1986, the owners of the Gold Hill Mill prepared the site for water storage in support of milling <br /> operations. The work included cleaning, surveying, and rehabilitating the upper level of the <br /> Times Mine, drilling a monitoring/pumping well into the Times Mine directly above the winze to <br /> the Wynona Mine, installing a concrete bulkhead with piping in the Times Mine, and installing a <br /> well casing into the Wynona Mine Shaft. The components are shown in Figure 2. The general <br /> proposed operations plan consists of pumping fresh water into Times Mine through the bulkhead <br /> and then pumping it out through the Wynona Shaft to the mill. Figure 3 provides a plan and <br /> profile view of the Times and Wynona mines. A key feature of the project that becomes apparent <br /> in the profile is the hydraulic connection between the Times and Wynona Mines. Through the <br /> Wynona Winze, 150 Level, and shaft, the two mines act as a single mine pool with drainage at <br /> the Times Mine bulkhead and an overflow at the Wynona Shaft collar. <br /> 600 S.Airport Road,Building A,Suite 205 <br /> Longmont,CO 80503 <br /> Phone: 303-651-1468•Fax: 303-651-1469 <br />